1. Field of the Invention
The present invention relates to wheel electronics in or for a tire control system of a vehicle for measuring a measurand and to a tire control system of this type.
2. Description of the Background Art
The present invention relates to systems for monitoring or determining tire-specific parameters, such as tire temperature, tire pressure, the rotational speed of a wheel, the profile thickness, etc. Systems of this type are generally called tire information systems, tire control systems, or also tire pressure control systems. The invention and its underlying problem are described hereinafter with reference to a tire pressure control system, but accordingly without limiting the invention.
Because vehicle safety and reliability are key factors in automotive technology, the tire pressure of vehicles must be checked regularly for safety-related reasons alone. This is frequently neglected. For this reason, modern motor vehicles have, inter alia, tire pressure control systems, which automatically measure tire pressure and are intended to detect early a critical deviation of the measured tire pressure from a desired tire pressure value. A manual check thus becomes unnecessary.
This type of tire pressure control system typically has at least one wheel electronics, assigned to a specific wheel, with a wheel sensor contained therein. This type of wheel sensor is designed to pick up a tire-specific parameter of a wheel assigned in each case to said wheel sensor and to transmit information derived from this measured value. The wheel sensor is integrated, e.g., into the rubber material of the tire; for example, it is vulcanized into the tire rubber. For the initial evaluation and relaying of the picked up information to be sent, the wheel electronics have a transmit antenna over which the information is transmitted. On the vehicle side, the tire pressure control system has at least one receiving device, which picks up the signals transmitted by the tire electronics with the information contained therein and relays them to a central arithmetic logic unit.
A typical bidirectional data communication occurs between respective wheel electronics and the vehicle-side receiving device assigned to it. In said bidirectional data communication, which occurs, for example, according to a known challenge-response method, the vehicle-side base station first sends a request signal (challenge) to the wheel electronics via a transmitting device and the wheel electronics sends back a response signal (response) to this request.
A general problem in tire pressure control systems results from the wireless communication between the wheel electronics and vehicle, which necessitates a local power supply on the part of the wheel electronics. In many tire pressure control systems, the wheel electronics is therefore equipped with a battery or an accumulator. To assure the lowest possible power consumption and thus to spare the tire electronics battery, measurement in the measuring sensor is not continuous but occurs in response to the appropriate request. For this purpose, the base station sends a command (i.e., request) for air pressure measurement to the wheel electronics.
The wheel electronics prompts the wheel sensor to make a measurement, provided it recognizes the command as such.
Because of the wireless transmission path between the vehicle-side transmitter and wheel-side receiver, transmission errors can occur with the transmitted request signal, however. For example, interfering pulses and signal dips can occur in the request signal. Interfering pulses can be caused, for example, by other signal sources, for example, by transmitting devices from other traffic participants in the immediate vicinity of the tire pressure control system, or perhaps also by other radio signals, which are superimposed by the transmitted request signal and interfere with said signal. Moreover, such interfering signals can also arise due to signal sources within the vehicle and be superimposed by the request signal in an undesirable way. Signal dips, in contrast, arise, for example, when the wireless interface is interrupted between the vehicle-side transmitter and the wheel-electronics-side receiver at least at times or in sections. These signal dips can occur when, for example, the tire pressure is to be measured at high speed. In this case, the wheel sensor attached to the tire has only little time to establish data communication with the vehicle-side transmitter/receiver and to perform a data communication. In addition, the body of the vehicle itself can also function at least partially or in sections as a screen for the transmitted request signal.
If a request signal is subject to more or less intense signal dips or interfered with by interfering pulses, a request in the request signal can then not be recognized as such. As a result, this means that the measuring sensor cannot perform any tire pressure measurement. This is a situation that should be avoided as much as possible during tire pressure measurement particularly for safety-related reasons.